Hitherto, a mechanism that performs shifting by switching a hydraulic circuit by switching a solenoid between excited and non-excited states has been used to control shifting of automatic transmissions for vehicles. In this technology, a fault detection device has been known which is configured to detect a fault of a solenoid valve by electrically detecting the occurrence of an abnormality such as a wire breakage failure and a short circuit failure of a solenoid. In this technology, there is known a detection method in which a duty ratio for determination is set on the basis of a set duty ratio that serves as a target value in the case of a short circuit between terminals of a linear solenoid, a current for energization of which is controlled through PWM (Pulse Width Modulation) control, and a short circuit between terminals is determined in the case where the set duty ratio, which is set so as to reach the target value through feedback control, becomes less than the duty ratio for determination.
If it is attempted to precisely set the duty ratio for determination in the detection method, it is difficult to lower a target current for the linear solenoid, which may disadvantageously restrain the control range of a current for the linear solenoid. Thus, there is proposed a solenoid abnormality detection device with improved detection precision that can detect a short circuit abnormality of a linear solenoid without depending on the duty ratio of PWM control (see Patent Document 1). The solenoid abnormality detection device includes a voltage monitoring circuit that monitors a voltage applied to the linear solenoid, and is configured to compare the voltage which is monitored by the voltage monitoring circuit and a determination threshold set on the basis of a power source voltage of a power source that supplies power to the linear solenoid to determine a short circuit abnormality of the linear solenoid on the basis of the comparison results.